Mean-Field and Second-Moment Budgets in a Baroclinic, Convective Boundary Layer

Lenschow, Donald H.; Wyngaard, J. C.; Pennell, W. T.

doi:10.1175/1520-0469(1980)037<1313:mfasmb>2.0.co;2

Cited by 440 publications

(341 citation statements)

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“…Rannik (1998) reached this conclusion with eddy-covariance data collected in the roughness sublayer over a Scots pine forest in Finland. Similarly, Lenschow et al (1980) found that the presence of horizontal temperature gradients greatly influence the mean temperature and momentum budgets, while only slightly affecting the second-moment budgets.…”

Section: Assessment Of Self-correlationsupporting

confidence: 73%

Similarity Scaling Over a Steep Alpine Slope

Nadeau

Pardyjak

Higgins

et al. 2012

Boundary-Layer Meteorol

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In this study, we investigate the validity of similarity scaling over a steep mountain slope (30-41 • ). The results are based on eddy-covariance data collected during the Slope Experiment near La Fouly (SELF-2010); a field campaign conducted in a narrow valley of the Swiss Alps during summer 2010. The turbulent fluxes of heat and momentum are found to vary significantly with height in the first few metres above the inclined surface. These variations exceed by an order of magnitude the well-accepted maximum 10 % required for the applicability of Monin-Obukhov similarity theory in the surface layer. This could be due to a surface layer that is too thin to be detected or to the presence of advective fluxes. It is shown that local scaling can be a useful tool in these cases when surface-layer theory breaks down. Under convective conditions and after removing the effects of self-correlation, the normalized standard deviations of slope-normal wind velocity, temperature and humidity scale relatively well with z/Λ, where z is the measurement height and Λ(z) the local Obukhov length. However, the horizontal velocity fluctuations are not correlated with z/Λ under all stability regimes. The non-dimensional gradients of wind velocity and temperature are also investigated. For those, the local scaling appears inappropriate, particularly at night when shallow drainage flows prevail and lead to negative wind-speed gradients close to the surface.

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Section: Assessment Of Self-correlationsupporting

confidence: 73%

Similarity Scaling Over a Steep Alpine Slope

Nadeau

Pardyjak

Higgins

et al. 2012

Boundary-Layer Meteorol

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“…In fact, τ ww was estimated assuming the isotropy hypothesis: τ ww = (2/3) e * (Nieuwstadt et al, 1992). Despite the discrepancies in the upper half of the CBL, the results obtained here are similar to Schmidt & Schumann (1989), who found that their results fitted better to the experimental data provided by Lenschow et al (1980). The dimensionless horizontal velocity component variances, u 2 /w 2 * and v 2 /w 2 * , (Figs.…”

Section: Vertical Profile Of Variancessupporting

confidence: 85%

“…The vertical profiles of wind velocity variances followed the results available in the literature (Lenschow et al, 1980;Schmidt & Schumann, 1989). Even though the vertical profile of potential temperature and pollutant concentration variances presented a similar maximum at the top of CBL, the behavior of the pollutant did not follow the pattern obtained for the potential temperature (Kaimal et al, 1976).…”

Section: Resultsmentioning

confidence: 54%

Pollutant transport in a Convective Boundary Layer with LES

et al. 2006

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ABSTRACT. This work describes the statistical properties of a Convective Boundary Layer (CBL) and the associated turbulent transport of a passive and inert pollutant, continuously emitted in the atmosphere by an area-source on the surface. The CBL flow and properties are simulating with a Large Eddy Simulation (LES) model. To assure the development of a quasi-steady turbulent regime, both the stability parameter and the Turbulent Kinetic Energy (TKE) criteria were applied to LES with similar RESUMO. Este trabalho descreve as propriedades estatísticas de uma Camada Limite Convectiva (CLC) e o transporte turbulento de um poluente inerte e passivo, emitido continuamente por uma fonte do tipoárea localizada na superfície. As propriedades da CLC são simuladas numericamente com o modelo de simulação direta dos grandes turbilhões (LES). A determinação da condição de quase-equilíbrio realizada com base no parâmetro de estabilidade para a CLC mostrou-se equivalente ao procedimento padrão, que utiliza os valores da energia cinética turbulenta integrada na camada. A estrutura vertical da concentração do poluente, temperatura potencial, e dos respectivos fluxos turbulentos e variâncias estão de acordo com os prognósticos da teoria da similaridade para a camada de mistura. Os parâmetros de assimetria da flutuação de concentração do poluente e da velocidade vertical refletem o padrão assimétrico das estruturas na CLC e indicam a importância dos processos de entranhamento na limpeza da camada. Palavras-chave:Modelo LES, Camada Limite Convectiva, Dispersão de Poluentes, Modelagem Numérica.

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“…In fact, over heterogeneous terrain with inhomogeneous surface heating, measurements indicate that U (z), σ 2 w , and also the scalar variances have strong spatial variability (LeMone et al 2003). The vertical velocity fluctuations tend to be of a higher magnitude over the arid patches, resulting in localized maxima in turbulent scalar fluxes (e.g., Lenschow et al 1980;Young 1988).…”

Section: Introductionsupporting

confidence: 67%

“…This provided the impetus for the current investigation, which considered the hypothesis that a key physical process underlying this phenomenon is an increase in the vertical velocity variance coupled with increased air temperature over the arid patches, resulting in a localized increase in turbulent sensible heat flux, identified earlier by Lenschow et al (1980) and Young (1988) for similar conditions.…”

Section: Discussionmentioning

confidence: 61%

Evaluating Source Area Contributions from Aircraft Flux Measurements Over Heterogeneous Land Using Large-Eddy Simulation

Bertoldi

Kustas

Albertson

2012

Boundary-Layer Meteorol

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The estimation of spatial patterns in surface fluxes from aircraft observations poses several challenges in the presence of heterogeneous land cover. In particular, the effects of turbulence on scalar transport and the different behaviour of passive (e.g. water vapour) versus active (e.g. temperature) scalars may lead to large uncertainties in the source area/fluxfootprint estimation for sensible (H ) and latent (LE) heat-flux fields. This study uses largeeddy simulation (LES) of the land-atmosphere interactions to investigate the atmospheric boundary-layer (ABL) processes that are likely to create differences in airborne-estimated H and LE footprints. We focus on 32 m altitude aircraft flux observations collected over a study site in central Oklahoma during the Southern Great Plains experiment in 1997 (SGP97). Comparison between the aircraft data and traditional model estimates provide evidence of a difference in source area for turbulent sensible and latent heat fluxes. The LES produces reasonable representations of the observed fluxes, and hence provides credible evidence and explanation of the observed differences in the H and LE footprints. Those differences can be quantified by analyzing the change in the sign of the spatial correlation of the H and LE fields provided by the LES model as a function of height. Dry patterns in relatively moist surroundings are able to generate strong, but localized, sensible heating. However, whereas H at the aircraft altitude is still in phase with the surface, LE presents a more complicated connection to the surface as the dry updrafts force a convergence of the surrounding moist air. Both the observational and LES model evidence support the concept that under strongly advective conditions, H and LE measured at the top of the surface layer (≈50 m) can be associated with very different upwind source areas, effectively contradicting surface-layer self-similarity theory for scalars. The results indicate that, under certain environmental conditions, footprint models will need to predict differing source area/footprint contributions between active (H ) and passive (LE) scalar fluxes by considering land-surface heterogeneity and ABL dynamics.

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Mean-Field and Second-Moment Budgets in a Baroclinic, Convective Boundary Layer

Cited by 440 publications

References 0 publications

Similarity Scaling Over a Steep Alpine Slope

Similarity Scaling Over a Steep Alpine Slope

Pollutant transport in a Convective Boundary Layer with LES

Evaluating Source Area Contributions from Aircraft Flux Measurements Over Heterogeneous Land Using Large-Eddy Simulation

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